An air bearing refers to a bearing that supports a load by lifting a rotating shaft due to the pressure of air compressed between the rotating shaft and the bearing.
In the air bearing, when viscous gas such as air, which is moving along with a moving surface, meets a stationary surface and is compressed, the pressure of air between the moving surface and the stationary surface rises to lift upward the moving surface.
Examples of the air bearing include a thrust air bearing for supporting a load applied in a longitudinal direction of the rotating axis and a journal air bearing for supporting a load applied in a radial direction of the rotating shaft.
A journal foil air bearing, which is a type of journal air bearing, uses a thin foil in order to more easily create pressure and improve dynamic stability at a high speed.
FIG. 13 illustrates a conventional journal foil air bearing 1. The conventional journal foil air bearing 1 includes a top foil 2 that is located to face an outer circumferential surface of a rotating shaft F that rotates in a preset rotation direction W and surrounds the rotating shaft F and a bump foil 3 that is an elastically deformable member having a wave shape and is located to surround the top foil 2. One end portions of the top foil 2 and the bump foil 3 are welded to a welding portion 4 on an inner surface of a bearing housing S.
Although the conventional journal foil air bearing 1 may more easily perform dimensional control because the number of parts is relatively reduced, the conventional journal foil air bearing 1 has problems in that it is very difficult to mount or disassemble the conventional journal foil air bearing 1 on the bearing housing S and it is also very difficult to store and manage elements, that is, the op foil 2 and the bump foil 3, of the conventional journal foil air bearing 1 in a workplace.
The conventional journal foil air bearing 1 also has problems in that since the bump foil 3 is directly mounted on an inner circumferential surface of the bearing housing S and the inner circumferential surface of the bearing housing S has to be processed to have a certain roughness as well as a size dimension, a specific process such as grinding or coating has to be additionally performed on the inner circumferential surface of the bearing housing S, thereby increasing total product costs.
In order to solve the problems of the conventional journal foil air bearing 1, a sleeve bearing in which the top foil 2 and the bump foil 3 are assembled in advance and modularized on an inner circumferential surface of a sleeve having a metal ring shape and then is assembled on the bearing housing S has been suggested. However, the sleeve bearing still has problems in that since the sleeve is added, a tolerance between parts has to be more precisely managed.
Although the top foil 2 and the bump foil 3 of the conventional journal foil air bearing 1 are fixedly welded onto the inner surface of the bearing housing 5, the top foil 2 and the bump foil 3 may be fixed by using any of various other methods, for example, by using a key or by using bolts and pins. However, such methods have problems in which technical uncertainty, difficulty in an assembling/disassembling process, and product costs are increased.